Changing head gasket

Tiny
JOAQUIN ARROYO
  • MEMBER
  • 1999 VOLKSWAGEN JETTA
  • 115,000 MILES
I have two questions #1 I did not do a compression check but I suspect a blown head gasket, car overheated several times and there is oil in the coolant and there is water in the oil am I right with my diagnosis? Also I considered it might be a crack block or head. But I didnt think it was those two because the car runs fine, the only thing wrong is water disappers from the coolant resovoir to the oil I find the water on the dipstick. Second question is since im going with replacing the head gasket I already started taking everything apart. Is it neccessaty to bring the motor to top dead center during this procedure? Couldnt I unbolt everything the way the motor is now and during removal make sure the the cams dont move and timing spockets dont move? And replace the head gasket throw everything back together and start it up? Also my car is a glx model it comes with a vr6 motor
Saturday, September 29th, 2012 AT 4:54 AM

11 Replies

Tiny
CARADIODOC
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Head gasket is the most likely suspect. There are some other tests that could have been done but they most likely wouldn't have identified the source of the leak. Those tests are more for combustion gases in the cooling system and coolant in the tail pipe.

You don't have to have it at top dead center when taking it apart but you will when putting it back together. Do you know what is meant by an "interference" engine?
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Saturday, September 29th, 2012 AT 5:06 AM
Tiny
JOAQUIN ARROYO
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Yes I know what interference engine is and I know I have that type of motor. But my concern is if I take it apart without letting the cams move, couldnt I put it back together the same way? Or are you saying I must retime the motor upon installation of head gasket
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Saturday, September 29th, 2012 AT 5:36 AM
Tiny
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The cylinder head will probably need to be re-surfaced (due to being warped)
which means that the Machine shop will want to have the head "stripped
down".

Take it apart "as is", but if you rotate it to TDC, you will not have
to worry about the bottom end when you put it back together.

Keep tension on the upper chain when you remove it from the cam gears
so that it does not slip out from the intermediate shaft sprocket.

Thomas
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Saturday, September 29th, 2012 AT 6:09 AM
Tiny
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Sorry, forgot to mention that you have an oil cooler... it could be
that the oil cooler is faulty, but the fact that you said it overheated
a few times, probably resulted in the head gasket (or head warp) failure.

You can remove the oil cooler and test it BEFORE you pull the head.

I tested this one with compressed air:

http://www.youtube.com/watch?v=WNYx4Xjr8-I&feature=plcp

Not out of a VR6, but the coolers are pretty much the same.

Thomas
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Saturday, September 29th, 2012 AT 6:18 AM
Tiny
CARADIODOC
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Unless you make something to hold the camshaft in position it is likely going to rotate due to valve spring pressure. It's too much work to try to maintain the relationship while everything is apart. Even if you could, you'd still want to recheck the timing so you're going to be rotating the crankshaft. It's easiest and fastest to just put the crank and cam at TDC, then install the head.
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Saturday, September 29th, 2012 AT 7:02 AM
Tiny
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HI ALL YOU MAY FIND CRACKS IN THE HEAD AND HAVE TO REPLACE IT.I WOULD JUST REPLACE THE HEAD WITH A REBUILT 1. GL
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Saturday, September 29th, 2012 AT 4:57 PM
Tiny
JOAQUIN ARROYO
  • MEMBER
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Thankyou for all the help you guys this would be my first head gasket replacment. One last question according to alldatadiy I need to Position crankshaft at oscillation damper retaining screw in engine cranking direction to marker TDC cyl 1 arrow. My question is if I just turn the crank until the arrow meets the marker would that really bring the number one piston to top dead center? In seems like all data is missing something here. Woulnt the proper procedure be put a compression tester on the number one cyl, crank it untill the guage reads pressure? Like I said this is my first head gasket any advise would be helpful I want to do this right. And to cardiodoc they advise me to buy a special tool to hold cams in place.
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Saturday, September 29th, 2012 AT 7:54 PM
Tiny
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The mark on the front crank pulley will not be enough. You need
to check that the camshafts are in the correct position via a
camshaft ruler (some coll it a cam lock tool).

Picture is attached.

Thomas
Image (Click to make bigger)
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Saturday, September 29th, 2012 AT 9:43 PM
Tiny
CARADIODOC
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Yup, but the cam holding tool is for assembling the engine. You were originally asking about taking it apart. If it isn't all the way apart yet you might want to set the crank at top dead center, then take a few pictures of the other pulleys. Use some paint to make the marks more visible if necessary.

A good way to start reassembling is to bring one piston to top dead center, back it up a little so no piston is all the way up, then you can install and torque the head knowing no open valve will hit a piston. Rotate the cam sprocket so it's at top dead center, then back it up too about the same amount. THAT can be easier said than done, especially if you're fighting with two camshafts. The point is no matter where you turn the cams, no valves will be hitting a piston. When everything is close and the timing belt is installed, THEN you can slowly turn the crank forward by hand to top dead center, then check how many teeth you're off on the other sprockets. If you feel a clunk in the crank, stop, back up, and reset the cam sprockets, then slowly try again. When everything appears to be correct, rotate the crank forward two revolutions, stop at TDC, then recheck all the timing marks. During those two revolutions you'll feel the intermittent resistance of a piston coming up on top dead center on the compression stroke, and if you turn it slow enough that pressure will leak out and the crank will start turning easier. That resistance to turning is gradual and soft, and feels a lot different than a valve hitting a piston.

If you loosen the timing belt to move it a few teeth on a sprocket, a camshaft can get away on you due to valve spring pressure pushing on a lobe. If you fight with that more than a few minutes you may want to find that holding tool you mentioned. I watched a former student struggle for hours with a GM engine with four camshafts, and once he borrowed the fixture from the dealer, the job took less than an hour.
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Sunday, September 30th, 2012 AT 1:34 AM
Tiny
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Hi all I would pull the #1 spark plug and turn it over. When I felt compression on the hole. I would use a pencil in the hole. Keep turning the crank until the #1 piston is all the way up. Then look at the timing marks. They will be close. Just line the marks and youll be on compression stoke on #1 CYL. Gl
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Monday, October 1st, 2012 AT 12:46 AM
Tiny
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With the valve cover off, turn the engine till the cams can be locked
with a couple of small plates.

The plates don't need to stay in, they are just used to verify #1 TDC.

https://www.2carpros.com/images/external/TimingChain9.jpg

As long as the upper chain does not slip out of the intermediate
gear... and you mark the cam gears to the upper chain, no worries
with loss of timing.

Thomas
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Monday, October 1st, 2012 AT 1:15 AM

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